In the previous forum, tile ideas were thrown around. Ideas about healing tiles that instantly healed anyone on it except undead, as well as the reverse of this.
Now, my own tile idea:
Water (yes, I know its there already): Water should remain pretty much the same, except that it should cure being on fire (and kill efreets) and acid (as the water neutralizes the acid as well as wash it out), it should have one other particular effect: it should stop magical projectiles, mainly spells and their effect (ie, spells won't effect you while in water, not even fireball). This does not apply to magical bolts and meléé effects.
Tar/Deep mud/: A tile that puts a -1 speed penalty on land movement. Otherwise acts like floor.
Also, what about formations? The old poll in the middle of the room is, in all honesty, getting a little old and hardly used. What about a poll with a well in the middle? Or a hallway filled with a certain tile? I believe those are on schedule for 2.0.
Healing tiles don't sound different enough from healing fountains to warrant doing, I think, unless it's something that would affect npcs only.
The mud idea is a good one though. Something that's not dangerous at all if there are no enemies around, but it'd probably even worse than getting caught in lava if a bunch of dangerous monsters showed up.